Fluid flow classifier



March 3, 1970 F. KAISER ETAL 3,498,453

FLUID FLow OLASSIFIER Filed Oct. 10, 1967 2 Sheets-Shut 1 FIG.1 l6

INVENTORS. FRITZ KAISER y ERNST ZIELINA AT TORN EYS March 3, 1970 KAISER ErAL 3,498,453

FLUID FLOW CLASSIFIER Filed Oct. 10, 1967 2 Sheets-Sheet .2

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FRITZ KAISER y ERNST ZIELINA ATTORNEYS United States Patent O ABSTRACT OF- THE DISCLOSURE An apparatus for classifying mixtures of fine and coarse materials by the use of a rotatable classifying wheel and an air flow which is caused to stream into a liner surrounding the classifier wheel, a pair of annular gaps at the periphery of the wheel and then in through the classifying wheel. During the rotation of the classifying wheel and the flow of air through theclassifier, the mixture of fine and coarse materials is carried from a spot located at the liner surrounding the classifying wheel around and to the periphery of the wheel. The fine material is carried through the wheel and discharged out along its axis, while the coarse material is carried around on the inside of the liner and discharged from the upper part of the liner after being carried nearly around to the point where material enters.

CROSS-REFERENCE TO' RELATED APPLICATION This application corresponds to German patent application No. A 46,021 filed May 12, 1964, on which no patent has so farlbeen granted.

BACKGROUND THE INVENTION Field of the invention The invention relates to improvements in fluid flow classifiers designed to separate a particle size mixture into two fractions respectively above and below a defined cut size point and, in particular, to a classifier provided with a rotatable classifying wheel, which with the flow of a fluid through the classifier effects the classification of the material.

Description of prior art Already known is a classifier whose rotating classifying wheel, free from sub-assemblies, receives. the classifying air entering from outside through an adjustable array of guide vanes. The feed material is introduced through a 'slot and passed onto the inner face of this array of guide vanes; carried along on the former in a film-like layer it is repeatedly rinsed by the air which comes in through the guide vanes and thus purged from fine material. After having covered a path extending over about three quarters of the perimeter of the classifying chamber, the retained oversize material is skimmed'off and evacuated through a worm conveyor located parallel to the axis of the wheel. Note is alsomade of the FL Kaiser U.S. Patent No. 2,739,709.

A' drawback of this already known classifier is the time and labor consuming fabrication of the precisely adjustable guide vanes and narrow gaps required between the perimeter of the rotating end walls of the classifying wheel and the stationary housing. In addition to this, said gaps necessitate the provision of extra devices which allow them to be rinsed with air so as to prevent material from entering. Inrecycling air operation, the guide vanes are sensitive to deposits of fine powder originating from the recycling air that is not completely dedusted.

Thesedrawbacks and problems are eliminated by the present invention which is backed by the latest discoveries and findings according to which sufficient purging of the ice film of material carried along on the stationary classifying chamber liner can be obtained by blowing classifying air that must have an adequate axial component, on a smooth path, from two sides and preferably symmetrically, against the travelling layer of material being classified. The action of this blast produces, in the middle of the path, a fluff of fine powder, the individual grains of which it is composed, being vigorously whirled through and scavenged by the classifying air.

SUMMARY OF THE INVENTION The apparatus, as provided by the present invention and incorporating the new know-how, comprises a classifying-chamber liner that is substantially closed, that means, interrupted only by one opening for the discharge of the oversize material and other openings for the introduction of classifying fluid and the feed material. The liner, together with the rotating side discs of the classifying wheel, enclosing or defining two annular gaps through which the clean fluid enters to rinse the material to be classified as it is carried along on the inner face of the classifying-chamber liner, and to effect the classifying process inside the classifying wheel. The width of these annular gaps must be so dimensioned that the entering fluid presents a sufficiently rated axial flow component which allows the film of fine powder in the central path of the classifying-chamber liner to be closed together in a fluff-like manner and in cooperation with the peripheral component of the classifying air to be whirled up and purged thoroughly.

Generally applicable values for the width of the gaps cannot be given; however, in the majority of cases they will be slightly less than one-fourth of the inside width of the classifying wheel. But this gap width is substantially larger than that of the mentioned known classifier, due to the fact that in a classifier according to the invention, the whole of the classifying air; and not a volume of scavenging air that must be kept as small as possible, is passed simultaneously through the gaps. Since emphasis is no longer on extreme precision of fabrication, the production costs involved for the classifier of this invention are appreciably cut down.

Some known classifiers are fitted with a rotatable classifying wheel mounted inside a classifying chamber, and air is utilized for effecting the classification of mix tures of coarse and fine materials into coarse and fine fractions. However, as far as known, none of the classifiers of this type includes the following combination of features of the present invention:

(1) Introducing clean air into the classifying chamber, and not air laden with material to be classified;

(2) Introducing clean air symmetrically through annular gaps located at the respective sides of the periphery of the classifying wheel, between it and a liner surrounding the wheel; and a (3) Introducing the feed material to be classified int theclassifying chamber liner from a defined point and discharging the classified oversize coarse material immediately in advance of this point after it has covered a path extending over about three-fourths of the perimeter of the classifying chamber liner.

The invention includes other important features and advantages.

While air may, in most cases, be preferred as the classifying fluid, it is to be understood that the apparatus and procedure of the present invention may be used with other fluids, including other gases or liquids (particularly water) without requiring appreciable modifications which cannot be made readily.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings forming a part of this application repre- 3 1. sent by way of schematic illustration, a few embodiments ofthe present invention.

In the drawings:

FIG. 1 is a vertical sectional view taken along the line II-II of FIG.. 2 of one embodiment of the invention, in which classifying air is admitted to and flows through both of the annular gaps provided on the respective sides of the classifying wheel;

FIG. 2 is a partially diagrammatic sectional view taken on the line II of FIG. 1;

FIG. 3 is a view similar to that of FIG. 1 taken on the line IVIV of FIG. 4 illustrating a modification in which the material to be classified is introduced through an opening in the liner of the classifying chamber surrounding the classifying wheel;

FIG. 4 is a diagrammatic sectional view taken on the line III-III of FIG. 3; and

FIG. 5 is a diagrammatic broken sectional view of a classifying wheel similar to the classifying wheel of FIG. 4, except that it is provided with zigzag baflles.

DESCRIPTION OF PREFERRED EMBODIMENT OF FIGS. 1 AND 2 The embodiment of the classifier shown in FIGS. 1 and 2 comprises a housing 8 having on a base 9. The primary elements of the classifier are mounted on a door 1 readily attachable and detachable from the housing by devices not shown. A bearing mounting extends axially of the door 1 carrying a shaft 6 provided with a V-belt pulley 17. The shaft 6 is mounted in bearings 7 and carries the classifying wheel 2 which comprises a front disc wall carrying spaced radially-extending baffles 3 at its periphery, on which is mounted an annular wall, as shown in FIG. 1, leaving a large central outlet opening. The classifying wheel 2 is located in spaced relation to a liner which includes a door wall extending in front of and opposite the disc wall of the wheel 2 around its periphery and part-way along the opposite annular wall. The disc door wall of the liner is carried by the door 1 along with the wheel 2 and a wall separating the feed inlet 10 from the air inlet passageway 28.

The door 1 is circular and laps the housing as shown in FIG. 1. It and the other elements referred to above comprise an assembly which is readily removable from the housing for purposes of cleaning and control, thereby affording easy access both to the classifying wheel and the entire interior of the housing.

The classification of the mixture of fine and coarse solid particles takes place in the classifying wheel 2 in the spaces between the blades or baflles 3, and in the space around the wheel. Air as the classifying fluid is exhausted from the classifier through a port 4 along with the undersize classified material. The exhaust port 4 is associated with a suction duct 5 mounted in the housing wall to the right and extending into slightly spaced relation to the wheel 2. The duct 5 is connected to a fan or blower not shown for drawing the air through the classifier.

The classifying air is drawn into the classifier through the passageway 28 and its path or paths through the apparatus is indicated by lines carrying arrows beginning with the inlet line 11. The air entering the duct 28 passes through openings 12 in the adjacent disc wall of the liner 1 Wheel 2 to guard'annulr p zsaganstma'e tar bein 15. During operation with the air being induced by suction, and with the wheel 2 being rotated, clean air flows between the side walls of the wheel 2 and the side walls of the liner 15, through the annular gaps 14 from opposite sides and then into the wheel 2. (See alsov FIG. 3). The air passes inwardly through the classifying wheel 2 from its periphery to its central portion, from which it flows through the central exhaust port 4. Air flow of the branch 24 passes through the gap 25 between the inner end of the duct 5 and the wheel 2 and prevents infiltration of the material being classified, from falling into the gap while the classifier is being shut down. In addition, a comically-shaped collar 26 is provided on classifying sifted that might otherwise fall in. The collar 26 projects out beyond the vanes 13 toward the edge of the liner wall and provides an annular opening (34 in FIG. 3) for the inflow of clean air.

The mixture of fine and coarse material to be classified, shown by dotted line 16, coarse in small circles, finein dots, is fed in through the gravity channel 10, from which it falls through an opening 29 in the disc wall of the liner 15 and is subsequently accelerated to the peripheral velocity of the classifying'whe'elZ by the action of centrifugal blades 13 attached to the peripheral side portionsLof the wheel 2. The entering air carries the material through the near annular gap 14 into the zone 18 extending between the classifying chamber liner 15 and the' classifying wheel 2. The classifying air introduced from both sides of the wheel acts to bring the particles of the material close together in a fluff 20 formed on the inside cylindrical surface of the liner at the peripheryof the wheel, so that the material is whirled up by the centrifugal action and rinsed or stripped by the air flowing through annular gaps 14, around and through the wheel. v

The classifying wheel 2, rotating in the direction of the arrow in FIG. 2, extracts from the material constantly flung against it, the powder 21 with a particle size ranging beneath the cut size point, while only oversize material 27 is retained in the fluff. To increase its cleanliness, oversize material 27 can, either as a whole or partially, be forced to recirculate Several times. This is e.g. achieved by narrowing the exit slot 22 (FIG. 2) for oversize material 27 in the upper part of classifying-chamber liner 15 to such a degfe'e that it does no longer skim-off the entire fluff. This proves particularly efficient if using a zig-zag-classifying wheel, such as the wheel 2' having zigzag shaped channels provided by spaced radiallyextending zigzag bafl'les 3' as shown in FIG. 5, since, even in case of an increase in the circulating bulk of oversize material, the wheel does not change its cut size point. Coarse product 27 leaves the classifying-chamber liner 15 tangentially through exit slot 22 apparent on FIGURE 2 and is thereafter discharged through coarse product duct 23. Fine material 21 passes out from the central portion of the wheel 2, with the air flow, into the suction duct 5. The cut size point is adjusted by varying the rotational speed of classifying wheel 2 and altering the volume of classifying air 11 put through. The cleanliness of the undersize material is decided by the characteristics of classifying wheel 2. By incorporating certain zigzag assemblies, for instance the zigzag bafiles 3' as illustrated in FIG. 5, every desired cut size point can be achieved--of course, at cost of other advantages such as, e.g., throughput rate and pressure consumption.

The cleanliness of the oversize material is substantiallydetermined by feed rate and intensity of the whirling-up effect to which it is subjected and which can be influenced by varying the air velocity in gap 14.

The pressure conditions prevailing on the classifier shown in FIGS. 1 and 2, are as follows:

By exhaust branch 5 classifying air 11 is sucked off under the action of the negative, pressure required in accordance with design and operational characteristics of the classifier; it enters freely through openings 12. A suitable design of centrifugal blades 13 allows one to create, both in feeding channel 10 and in coarse product discharge duct 23, a slight negative pressure. that sucks some dedusting air in there, but permits admission and evacuation of material without air locka feature that presents considerable merits.

The mixture of fine and coarse material to be classified in the apparatus of FIGS. 3 and 4 is fed into the classifier through a feeding channel 30 passing here through an opening 35 in the top of classifyingechamber liner 15. The classifying air enters from outside through a channel 31 (line 11) and, after having passed through openings 12 and 34 (about the same as in FIG. 1) is accelerated by centrifugal blades 13 up to the peripheral velocityof classifying wheel 2 and flows along the sides of the wheel then inward through the two annular gaps 14. The material entrapped in the fluff formed there being close to gether, whirled up and rinsed by the classifying air 11 introduced from either side. After having taken its way through classifying wheel 2, the classifying air, together with undersize fine material 21 resulting from the separating process, leaves the classifier through central exhaust port 4 and suction duct 5. The oversize material, the path 33 of which is shown along classifying-chamber liner 15 in FIG. 4, is, in this example, carried out parallel to the axis, through worm 32. All further particulars of the classifier of FIGS. 3 and 4 correspond to those of FIGS. 1 and 2. In both embodiments the separated coarse material is carried to the upper part of the wheel and discharged at a point just short of the point where the charge is introduced into the classifier.

What is claimed is:

1. In a fluid flow classifier for effecting the classification of a mixture of coarse and fine particles in which the classifier is of the type including a housing, a rotatable classifying wheel mounted in said housing on a h rizontal axis and including a front disc wall carrying spaced radially-extending baflies on which an annular wall is mounted, feed channel means for feeding said mixture to the classifier, a discharge channel positioned immediately before the entry point of said feed channel means as viewed in the sense of rotation of the classifying wheel, for evacuating the coarse product, wherein the improvement comprises a liner in the housing having peripheral and side walls substantially surrounding the classifying wheel in spaced relation, said feed channel means communicating with the space between said liner and said classifying wheel, said liner side walls and the front and annular walls of said wheel defining two annular gaps, the side walls of said liner having openings therein, means for admitting clean classifying fluid to flow through said openings and then simultaneously through sa d gaps into the space between the periphery of the wheel and the liner, and therefrom into the classifying wheel between said bafiles, and means for conducting a stream of fluid carrying entrained fine particles from the central portion of said wheel through the central opening provided by said annular wall and from the classifier 2. A fluid flow classifier as claimed in claim 1, wherein the feed channel means for the material to be classified extends to a feed opening in the upper peripheral wall section of the liner.

3. A fluid flow classifier as claimed in claim 11, wherein the feed channel means for the material to be classified extends to a feed opening in the front wall of the liner and which defines in combination with the front wall of the classifying wheel located at that side, a downward gap for the passage of the material being classified.

4. A fluid flow classifier as claimed in claim 1, including centrifugal blades provided at the outer face of each of the walls of the classifying wheel.

5. A fluid flow classifier as claimed in claim 1, wherein the means for conducting the stream of fluid carrying fine particles from the central portion of the wheel comprises an exhaust duct located with its inner end spaced from the wheel to provide an annular gap.

6. A fluid flow classifier as claimed in claim 5, wherein said clean fluid admitting means comprises an admission channel located outside of the liner for feeding the clean fluid through the openings provided in the liner, to the annular gap defined by the liner wall and the outer edge of the front wall of the classifying wheel and into the annular gap situated between the liner wall and the outer edge of the annular wall of the classifying wheel positioned at that side.

7. A fluid flow classifier as claimed in claim 5, wherein the classifying wheel is provided with a conically shaped collar located adjacent to the gap between said duct and the wheel and extending outwardly over the gap toward the liner for preventing particles of material from entering said gap.

8. A fluid flow classifier as claimed in claim 7, wherein the liner includes a part extending inwardly in spaced relation to the annular wall of the wheel and to a point spaced somewhat from the outer edge of said conically shaped collar thereby providing an annular gap for the inflow of clean air to the classifying wheel.

9. A fluid flow classifier as claimed in claim 1, wherein said classifying wheel comprises radial, zigzag shaped classifying channels defined by the radially-extending baflles.

References Cited UNITED STATES PATENTS 2,739,709 3/1956 Kaiser 209144 3,089,595 5/1963 Kaiser 209'144 3,269,537 8/1966 Kaiser 209-144 2,3 67,906 1/1945 Wall 209144 FOREIGN PATENTS 694,219 7/ 1953 Great Britain. 1,007,440 10/ 1965 Great Britain.

FRANK W. LUTTER, Primary Examiner (2 2 3? UNITED STATES PATENT OFFICE March 3 1970 Inventor(s) Fritz Kaiser and Ernst Zielina It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 25, "on" after "having" has been canceled:

column 5, last line (claim 3-, line 1) 11" has been changed to --l-.

SIGNED AN'D SEAILEB L 1 4 I970 Amt:

Eawml M. Fletc J -BIA]! z.

Anesti g officer missioner or a nts 

